This invention is related generally to TiOx (titanium oxide) or titanium oxide TiO2 (titanium dioxide) coatings or films, products incorporating the TiOx coatings, methods for making the coatings and products, and an apparatus for making the coatings and products.
TiO2 is widely used in a number of applications. For example, TiO2 is used for UV filters in glazing and opthalmic applications, as a high index material in optical stacks, and as a photocatalytic coating to degrade organics on the surface of billboards and lighting fixtures. TiO2 is typically deposited at high temperatures by chemical vapor deposition (CVD) techniques. These CVD techniques, however, can not be used on low temperature substrates such as plastics or polymers, because the deposition temperatures will damage the substrate.
TiO2 has been deposited on low temperature substrates, such as some plastics, by conventional physical vapor deposition (PVD) techniques such as sputtering and e-beam evaporation. These PVD techniques, however, suffer from being very low rate processes, typically, 10-100 angstroms/minute. In addition, the TiO2 coatings tend to have a high tensile stress, thus limiting their usefulness in applications requiring thicker deposits, multi-layer stacks, and depositing on thin films where the stress may cause curling of the substrate. Also, these coatings tend to be rough with low absorbency per unit thickness (A/t) in the UV light range, where A is the absorbency and t is the thickness.
More recently, workers have tried to overcome the problems cited above by depositing TiO2 in plasma enhanced chemical vapor deposition (PECVD) reactors with and without biasing. These PECVD processes, however, have not overcome the limitations of the classical PVD approaches, and still generate low rate, highly stressed TiO2 coatings with low (A/t) in the UV light range.